Bead Width Prediction in Laser Wire Additive Manufacturing Process

in Mbodj, Natago Guilé; Plapper, Peter (Eds.) Bead Width Prediction in Laser Wire Additive Manufacturing Process (2021, October 22)

In laser wire Additive manufacturing (LWAM), the final geometry is produced using layer-by-layer deposition principle of beads. To achieve good geometrical accuracy of the final product, proper ... [more ▼]

In laser wire Additive manufacturing (LWAM), the final geometry is produced using layer-by-layer deposition principle of beads. To achieve good geometrical accuracy of the final product, proper implementation of the bead geometry is essential. The process parameters have a direct influence on the bead geometry, thus to the printed part. In this paper, we propose a bead width prediction model to improve deposition accuracy. A regression algorithm is applied to the experimental results to predict the bead width dimension. Bead prediction equation relating the bead width growth for each layer is obtained for a given set of process parameters. The prediction equations show similar evolution trends and confirm the influence of deposition process parameters on the bead width. The proposed method demonstrates a prospective insight on a more proper selection of process or physical parameter intervening in laser wire additive manufacturing process. [less ▲]

Value Stream Mapping (VSM) to Evaluate and Visualize Interrelated Process-Chains Regarding Circular Economy

in Advances in Production Management Systems. Artificial Intelligence for Sustainable and Resilient Production Systems (2021, August 31), 633

The concept of circular economy (CE) aims to close and slow resource loops without neglecting the goals of sustainable development. Recently, the concept received encouraging attention among researchers ... [more ▼]

The concept of circular economy (CE) aims to close and slow resource loops without neglecting the goals of sustainable development. Recently, the concept received encouraging attention among researchers and business experts to be a convenient solution to move away from the finite linear economy concept to a more sustainable solution. However, this change of paradigm is only possible if we consider systems in a holistic manner and can localize the preventing hurdles. Value stream mapping (VSM) is a commonly known lean method, used to develop current state visualization of product and information flows within organization, helping to seek weaknesses and improve process flows. The motivation of this paper is a new C-VSM model, which enables its users to evaluate and visualize connected process-chains regarding CE on different levels in a holistic manner. For this purpose, the traditional VSM model was adapted towards the needs and requirements of CE through the application of a new representation method, additional indicators, and an appropriated evaluation system. C-VSM is in line with the current political and industrial objectives to apply CE principles by enabling a holistic reflection and consideration of supply-chains (SCs) on different levels. The model itself is validated through an extensive cross-company case study. [less ▲]

Failure mechanism analysis based on laser-based surface treatments for aluminum-polyamide laser joining

in Journal of Materials Processing Technology (2021), 298

The development of strong metal to polymer assemblies is currently an important research subject thanks to its prominence to develop lightweight structures. Furthermore, laser welding is known to be a ... [more ▼]

The development of strong metal to polymer assemblies is currently an important research subject thanks to its prominence to develop lightweight structures. Furthermore, laser welding is known to be a fast, reliable, and versatile joining process, and it was demonstrated recently that it can be applied to such metal to polymer systems. To enhance the mechanical properties of the laser-joined aluminum-polyamide (Al-PA) specimens, laser polishing and laser ablation processes have been implemented on the aluminum surface before joining. The polyamide surface was also treated with the laser beam, separately. The surfaces were tested by several characterization techniques before and after each surface treatment. Then aluminum and polyamide samples with different surface treatments have been joined with an identical laser joining process. The mechanical properties of the joints in single lap shear configuration are reported and the failure mechanisms are discussed based on micro-computed x-ray tomography imaging of joined specimens and microscopic analysis before failure. Results show that both surface treatments of aluminum significantly improve the shear load of the joint; however, with different failure mechanisms. Polyamide surface treatment and increasing degree of crystallinity are effective when combined with the laser polishing of the Al surface. This combination is responsible for further enhancement of the shear load of the joint to the limit of base metal strength which is approximately 60 % improvement compared to the untreated samples. Finally, energy dispersive X-ray mapping shows the physicochemical bonding between aluminum oxide and polyamide at the interface. [less ▲]

Laser Welding of Metals to Polymers Under the Special Influence of Surface Pretreatment on Interfacial Thermal Transfer

Doctoral thesis (2021)

Joining of metals to polymers is increasing among various industries because of its ability to produce lightweight hybrid products with tailored properties. Common joining methods, such as adhesive ... [more ▼]

Joining of metals to polymers is increasing among various industries because of its ability to produce lightweight hybrid products with tailored properties. Common joining methods, such as adhesive bonding and mechanical fastening, require adding a third material which might involve hazardous chemicals or add extra weight and stress concentration points to the component. On the other hand, Laser-Assisted Metal – Polymer joining (LAMP) is a contactless, rapid, highly precise and energy-efficient technique, that produces autogenous and miniaturized joints. It was already demonstrated that surface pretreatment prior to the welding process has a significant impact on the joint performance by modifying surface chemistry and topography, promoting chemical bonding and mechanical interlocking. This research aims at expanding the understanding of the effects of surface properties on the joint’s performance by investigating their influence on interfacial thermal transfer. While increased surface roughness of metallic partner is expected to improve LAMP joint performance by promoting mechanical interlocking, it is hypothesized that a smoother surface would improve the joint quality by enhancing the interfacial thermal transfer during the welding process, resulting in a larger area of molten polymer at the interface and a better joint performance. In this research, aluminum (Al1050) and titanium (Ti64) were joined with polyamide (PA6.6). Initially, laser welding parameters were optimized and kept constant during all surface pretreatments’ investigations. Preliminary surface pretreatments, using short-pulsed laser ablation and atmospheric plasma pretreatment, were conducted on Al1050 – PA6.6 to analyze the effects of surface composition and topography on joint quality and performance, and to optimize interfacial adhesion. Results show a correlation between increased surface oxidation and surface energy with improved interfacial adhesion and joint resistance to shear failure. Compared to plasma pretreated surfaces, laser ablation of metals results in a very rough surface which exhibits perfect wettability to both water and diiodomethane. This promotes mechanical interlocking and interfacial adhesion, resulting in a relatively stronger joint failing in a cohesive failure mode. Results confirm that an improvement of the assembly’s shear resistance to failure can certainly be achieved without an increase in surface roughness and interfacial interlocking, as observed in case of plasma pretreatment. Design of Experiments (DoE) techniques were utilized for both material combinations in order to optimize laser ablation process and to investigate the effects of pretreatment parameters on surface properties, interfacial thermal transfer, joint quality and resistance to failure. Laser ablation parameters influenced the surface topography with no significant effect on the surface composition, and all laser-ablated surfaces showed perfect wettability to both water and diiodomethane. While all ablated surfaces demonstrate cohesive failure mode, smoother ablated surfaces results in a better interfacial thermal transfer as indicated by the Thermal Contact Resistance (TCR) calculations and measurements, based on Cooper–Mikic–Yovanovich (CMY) model and layered Laser Flash Analysis (LFA) investigations, respectively. Results show that a smoother ablated surface results in better interfacial thermal transfer, melting a larger area of polymer which increases the joint quality and resistance to shear load. [less ▲]

The effect of temperature and joining speed on the joining quality for conduction laser joining of metals to polymers

Scientific Conference (2021, June 24)

Laser joining of metals to polymers offers several advantages to produce lightweight hybrid assemblies. An important one is the exceptional control over the heat input which defines the temperature at the ... [more ▼]

Laser joining of metals to polymers offers several advantages to produce lightweight hybrid assemblies. An important one is the exceptional control over the heat input which defines the temperature at the interface of the materials. Initially, the in-situ heating observation of PA inside ESEM is considered. Then, aluminum and polyamide are joined in an overlap configuration while the temperature was recorded simultaneously at different areas between the materials. The results show that due to excessive heat input, polyamide degrades and leaves bubbles in the melted area. Finally, the materials are laser joined with several joining speeds to investigate different cooling rates of the polyamide during the joining process. It is concluded that joining with high cooling rates generates an amorphous melted layer of the polyamide which is different from the semi-crystalline structure of the bulk. This difference acts as a stress concentration zone and reduces the shear strength of the assembly. [less ▲]

Prediction of Cu-Al weld status using convolutional neural network

Scientific Conference (2021, June 21)

Welding copper (Cu) and aluminum (Al) result in brittle intermetallic (IMC) phases, which reduces the joint performance. The key for a strong joint is to maintain an optimum amount of Al and Cu ... [more ▼]

Welding copper (Cu) and aluminum (Al) result in brittle intermetallic (IMC) phases, which reduces the joint performance. The key for a strong joint is to maintain an optimum amount of Al and Cu composition in the joint. To implement this without the destruction of the sample is a challenge. For this purpose, high-resolution images of the weld zone are utilized after welding. With the image processing technique, the presence of (Al/Cu) material melted is distinguished. Therefore, the different weld type/status like insufficient melt, optimum melt, and excessive melt is detected from the images. This paper analyses the weld images and applies the convolutional neural network technique to predict the weld type. The microstructure and Energy Dispersive X-ray Spectroscopy (EDS) analysis of the fusion zone for each weld type are correlated to the weld images. [less ▲]

Correlation of Optical Signal During Laser Fusion Welding of Copper to Aluminum

in Journal of Laser Applications (2021, January 05), 33(1),

Laser joining of dissimilar metals, copper and aluminum, allows for the precise delivery of laser energy and high process speed. The keyhole-based process is very efficient for welding Al–Cu, considering ... [more ▼]

Laser joining of dissimilar metals, copper and aluminum, allows for the precise delivery of laser energy and high process speed. The keyhole-based process is very efficient for welding Al–Cu, considering the high reflectivity and thermal conductivity of the materials joined. For the Al–Cu system, the formation of detrimental intermetallic compounds is the main issue. Fusion welding with laser as a heat source involves the melting of metals. However, the high speed of the laser welding process is advantageous for terminating the excessive melting of Al and Cu and eventually controlling the detrimental intermetallic phases. Therefore, information pertaining to melted material is an important criterion for achieving joint strength. In this paper, the photodiode signal measured during the laser welding of Cu to Al is investigated as a process monitoring technique. In welding from Cu to Al, the melting of Al (bottom sheet) is very critical for joint strength. The amount of Al material that can be intermixed in Cu depends on the solubility limit of the Al–Cu system. The plasma plume emission during laser welding is used to extract the rapid melting of Al. This study shows the correlation of the Al characteristic peak at a wavelength of 396 nm with the shear strength of the joint. [less ▲]

New insights into the origin of fine equiaxed microstructures in additively manufactured Inconel 718

in Scripta Materialia (2021)

Fine equiaxed grain regions are frequently observed in additively manufactured Inconel 718 alloy. Based on a grain-to-grain orientation analysis using EBSD, many assemblies of neighboring grains in these ... [more ▼]

Fine equiaxed grain regions are frequently observed in additively manufactured Inconel 718 alloy. Based on a grain-to-grain orientation analysis using EBSD, many assemblies of neighboring grains in these regions have been found to display multiple-twins orientation relationships sharing common 〈110〉directions and exhibiting 5-fold symmetry. This is an experimental proof that the grain refinement observed in inconel 718 is due to Icosahedral Short-Range Order (ISRO) mediated nucleation mechanism. This is the first report of ISRO-mediated nucleation of fcc nickel which widens the perspectives on the microstructures control in additive manufacturing of Ni-based superalloys. [less ▲]

Holo Study – Mixed Reality Framework for Industrial Engineering Education and Training

in Trends in Technical & Scientific Research (2020), 4(5), 0131-0135

Nowadays, students struggle with understanding complex production processes and kinematics of machine tools and robots. While professors mostly have been dealing with these subjects for many years ... [more ▼]

Nowadays, students struggle with understanding complex production processes and kinematics of machine tools and robots. While professors mostly have been dealing with these subjects for many years, students have only short time to be introduced to the complex nature of these topics. Mixed Reality allows students to engage hands-on in their subjects to reach new dimensions of understanding. Making challenging topics for students accessible by creating a more visual and tactile experience. The applications for entertainment and gaming are off the charts, but the implications for augmented reality in education and science are also undoubtedly massive. The project focusses on making education as interactive as possible, which helps both, teachers and students receive a unique tool for communicating phenomena and processes that are difficult to describe verbally. As a result, a complex knowledge becomes simple, an involvement of students grows, the quality of education increases [less ▲]

WELDING COPPER TO ALUMINIUM WITH GREEN LASER WAVELENGTH OF 515 NM

Scientific Conference (2020, October 19)

Joining copper and aluminum sheets is difficult because of brittle intermetallic phases (IMP) formed in the joint, which results in reduced performance. The traditional approach to overcome this issue is ... [more ▼]

Joining copper and aluminum sheets is difficult because of brittle intermetallic phases (IMP) formed in the joint, which results in reduced performance. The traditional approach to overcome this issue is to irradiate the laser beam from Aluminum (Al) to control the weld depth and mixing of Cu in Al. The laser welding approach from the copper side (Cu on top) to Al is very sparse in the literature. In this paper, the welding approach from copper (top sheet) to aluminum is studied with green laser (515 nm) due to improved absorption at this wavelength. The objective of irradiating the laser beam from the copper side (Cu on top) is to exploit the higher solubility of Al in Cu (about 18%), which is significantly higher than Cu in Al. Therefore more Cu and Al can be melted and mixed in the joint for copper sheet placed on the top. From the tensile shear test, a strong joint is obtained with a fracture on the heat-affected zone (HAZ) of Al. Detailed microstructure and composition of Al and Cu in the joint is performed by Energy-dispersive X-ray spectroscopy (EDS) to investigate the composition in the joint. The EDS analysis indicates that a large amount of beneficial Cu solid solution and Al-rich phases is formed in the joint. The detrimental phases are intermixed in between the ductile phase composition i.e Al-rich and Cu solid solution. Therefore the effect of detrimental intermetallic phases is mitigated by intermixing with large ductile phases. With this paper, the fusion welding approach for joining Cu and Al system with a significant level of Cu and Al melting is shown. [less ▲]